This invention relates to cathode ray tube effusive material structures and more particularly to an improvement in the insulative means for supporting a container of effusive material within a cathode ray tube.
In cathode ray tubes of the type conventionally employed in image display applications, at least one effusive material structure, as for example, a getter, is affixed to the forward end of the electron generating assembly oriented within the neck portion of the tube envelope. An exemplary type of getter structure is one referenced within the art as an antenna getter, which conventionally includes a resilient longitudinal positioning member or wand having a curvature therein and a getter container terminally mounted thereon. Such antenna type structures are usually affixed to the anterior portion of the electron gun assembly, extending forwardly therefrom in an outward curving manner prior to the positioning of the assembly within the restrictive neck portion of the tube envelope. The curved wand, being a resilient member, exhibits flexure to facilitate insertion of the electron gun assembly into the neck portion, while assuring sequential orientation of the forward extending getter container in a position closely adjacent to the interior surface of the outwardly flared infundibular portion of the tube envelope.
It is conventional practice in the art to coat the interior surface of the funnel portion of the tube envelope, and the forward area of the integral neck portion thereof, with one or more electrical conductive coatings. In certain tube constructions, it is desirable to isolate the finally positioned getter from the respective funnel-disposed coating therebeneath. Such discrete positioning is achieved by the getter supportive means taught in U.S. Pat. No. 3,961,221, which is assigned to the assignee of the present invention. This patent discloses a wand type cathode ray tube getter structure having a discrete support means in the form of a rotatable member oriented at the forward end thereof. The rotatable member being formed as a wheel of insulative material, beneficially effects facile positioning and positive spatial supportive placement of the container relative to the wall of the envelope, and thereby minimizes abrasion of the coating on the interior surface of the tube during positioning therein. Upon final positioning, the insulative wheel desirably isolates the getter from the adjacent coated surface of the funnel. However, in some tubes it has been found that the forward oriented rotatable member may be within the path of the scanning electron beam or beams. In such cases, any build-up of electric charge accumulative on the insulative member tends to introduce display pattern distortion during normal scan operation of the tube. Additionally, there have been occasions when spurious depositions of effusive material on the rotatable member have diminished the insulative characteristics of the member.